"You've studied about pair production, of course."

"I flunked. Even with your help I flunked."

He smiled slightly. "Pair production takes place when a gamma radiation of the right energy passes close to a nucleus. The gamma radiation then changes into an electron and a positron. Conversely, when an electron and a positron collide, they produce a quantum of gamma radiation."

"This I know, but how and why?"

"How deep do you want to go into nuclear physics?"

"Not very. Just explain once more how pair production makes a matter transmitter possible."

Peter said, "Not very long after pair production was found to be a fact in cloud chamber photographs, the nuclear physicists began to compute the energies that might be needed for pair production of nuclear particles. If pair production took place between the lighter particles, it should take place among the heavier particles providing the gamma radiation was energetic enough. Sure enough, when they built the super-accelerators, they found that they could produce proton pairs and neutron pairs. Then someone caught sight of an alpha pair being produced and that started the construction of the super-super colossal accelerator, in which they caught the pair production of lithium nuclei, and then beryllium, and then came a sprinkling of the next few higher nuclear weights. They even got a couple of sodium nuclei from the first attempts.

"Somewhere in here they discovered that each atom had its own resonant frequency, and that if you bombarded the nucleus with that resonant frequency the result would be half a pair's worth of resulting gamma."

"That's where I always get lost. First you bombard your junk with gamma, and cause it to break up into more gamma, which doesn't seem quite right."

Peter laughed. "This is the easy part," he assured her. "The gamma from my bombarder is absorbed in the production of the half-pair; the resulting radiation can be sent in a tight beam by means of a parabolic reflector, coated with one of the semi-conducting elements, through which a rather high current is being passed. Otherwise the radiation is so hard that it just goes through anything. When the tight beam hits a second parabolic reflector of similar construction, the hard gamma is focussed to an atomic point and the nucleus re-forms. In other words, if I break up a nucleus of iron, for instance, into 

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